Women with stressful jobs are risking their health as much as they would if they smoked or took no exercise, researchers have found.

The study assessed the impact of job strain on the health of 21,290 female nurses in the US using a series of questionnaires.

Personal characteristics, job content and health status were measured and compared over a four-year period.

The results showed that the women most at risk of ill health were those in jobs that were very demanding, but in which they had little control.

The health risks were further exacerbated if the women had little social support on which they could rely.

In fact, for women in this situation, the impact on health was a great as that associated with smoking and sedentary lifestyles.

The researchers, from Harvard School of Public Health in Boston, conclude that employers need to find more effective ways to reduce job strain for staff.

They say that current techniques, such as relaxation therapy tend to target individuals and their symptoms.

A more effective strategy would be to tackle the job environment.

Lead researcher Dr Ichiro Kawachi told BBC News Online: "We already know that the health status of smokers and sedentary people deteriorate more quickly than non-smokers and exercisers.

"Our study shows that job strain among female nurses has a comparable effect."

Culture changed needed

Research shows there is a strong link between ill health and stress in a range of occupations

Professor Cary Cooper, University of Manchester Institute of Science and Technology

Professor Cary Cooper, an expert in occupational stress at University of Manchester Institute of Science and Technology, said a major culture change was needed among employers to tackle the problem of work-related stress.

He said there was an increasing body of evidence to show that workplace stress had a significant impact on health.

In the UK, workers were increasingly having to cope with long hours, heavy workloads, autocratic bosses and a lop-sided balance between home and work - all of which contributed to growing stress levels.

Research by his own department had shown that one in ten workers felt bullied by their bosses.

Professor Cooper told BBC News Online: "We have to ensure that organisations know that it is not just helping individuals to cope with the changing nature of work that is important, but getting senior managers to change the whole culture of the organisation."

Professor Cooper said some employers were reluctant to make such changes, but they had to realise that the long-term impact of stress was costing them a fortune - both in sick days and lost productivity.

The Health and Safety Executive is currently considering proposals for a code of practice on dealing with stress in the workplace.